Field of the Invention
This application describes embodiments of apparatuses, methods, materials, methods of manufacture, and systems for the treatment of wounds, specifically to aid in packing and treating wounds.
This application further relates to improved wound dressing materials. In particular this application relates to wound dressing materials with improved drapeability, which allows them to more easily conform to the shape of a surface over which they are placed. Especially, but not exclusively, the present application relates to foam materials, especially those suitable for use in negative pressure wound therapy (NPWT).
Description of the Related Art
Wound dressings are commonly manufactured from sheet materials. These materials include transparent films and adhesives and opaque foams and fibres. These materials generally retain their transparency or opacity upon fluid absorption, the exception being carboxymethylcellulose-based hydrofibre (which is initially opaque and becomes transparent when wet). Wound dressings which rely upon a foam element for exudate management are opaque and require removal and exchange for a new dressing during every wound inspection. This is a disadvantage of opaque dressings, for example, including a foam element. Foam-based dressings also have limited extensibility due to the mechanical properties inherent in a material of foam structure; this can cause problems when attempting to dress locations of high curvature. In spite of these performance disadvantages, the use of foam-based wound dressings or dressing elements dominates woundcare. This may be due to their excellent absorbency, low dry weight, cut-ability and mouldability. Limited extensibility is not restricted to foams; this is also a property of the films commonly applied in medical devices.
The single-axis lattice cutting of monolithic materials, including the sheet materials utilised in wound dressings has been disclosed in (GB821,959). However, once cut, these materials are not extended in any manner until post-application to the wound, and only then as a result of the flexing of the limb or other part of the body on which the dressing is worn. Whilst this type of dressing does enable some ease of movement for the patient, the material only permits minimal visibility of the wound. Additionally, the size of apertures and thus the permeability of the material, particularly important for the release of exudates from the wound, cannot be controlled.
There is a need for a wound dressing which can be established in an extended conformation both prior to application and during application to a wound.
There is a need for a wound dressing which can be retained within a defined extended conformation both prior to application and during application to a wound.
There is a need for a wound dressing which allows visualisation of the wound immediately upon application of the dressing.
There is a need for a wound dressing which has a controlled aperture profile, which enables control of exudate egress.
There is a need for a wound dressing which has a controlled contractile profile for promoting wound closure.
NPWT is a relatively new treatment for open wounds. Typically in NPWT the wound cavity or surface is filled or covered with a material that allows the transmission of a partial vacuum (i.e. does not completely collapse) to the wound bed when a negative pressure is applied to the wound area, and also allows fluids to pass from the wound bed towards the source of negative pressure. There are two primary approaches to NPWT, gauze or foam types. The gauze type (also referred to as the Chariker-Jeter technique) involves the use of a drain wrapped in gauze topped by a sealed dressing. The foam type involves the use of foam placed over or in the wound. The present invention is directed primarily, but not exclusively, towards the foam type of NPWT.
In foam based NPWT the wound is filled or covered with a porous, compressible foam packing material and covered over and sealed with flexible sheet (a drape) that is fairly impermeable to fluids. A tube is inserted under or through the drape into the wound site and its distal end is connected to a vacuum source (commonly a pump). The wound cavity, enclosed by the drape and tissue, contracts under the force of atmospheric pressure and compresses the packing material visibly. Gross tissue movement ceases after a few tens of seconds and fluid flow from the wound (withdrawn from the tissue) ensues. The fluid is transmitted through the packing material and up the vacuum tube to a collection receptacle positioned between the distal end of the tube and the vacuum source. The material mechanically supports the tissue to which it is applied, and also allows the free flow of fluids away from the site when a vacuum is applied, even when compressed. A good material for this application is hydrophobic, reticulated polyurethane foam of very high free internal volume. However, articles of high free internal volume tend to be poorly drapeable due to the requirement for their structure to mechanically support their high free internal volume, and this is the case in current foams applied in NPWT.
The foams, which in other regards are near optimal for NPWT, are very poorly conformable to the site of application especially prior to the application of a covering drape and vacuum being applied. This is true for cavity wounds of concave geometry, and surface wounds, e.g. to the extremities, of convex geometry.
Monolithic articles of high free internal volume are able to support their own external dimensions by virtue of their mechanical properties, i.e. they are relatively stiff. This factor has the side effect of making such solid objects poorly drapeable and this is not desirable for all applications. For some applications, the mechanical integrity of the structure is not required at the scale of the monolith itself.
For medical applications involving the application of articles to the body, both good drapeability and good resistance to compression under loading are desirable attributes.